Currentposition

Research interests

How organisms adapt to novel environments, as single genotypes and as complex communities, is one of the key questions in biology and central to my research. In a mix of fundamental and applied projects, my research sheds light on this basic question, and at the same time aims to develop applications addressing problems in society such as the development of indigenous knowledge and the spread of antibiotic resistance. Central themes in my research include evolution of interaction between microbes, the dynamics of adaptation and speciation, the role of sex in evolution and the study of microbial communities within fermented products.

Fitness effects and epistasis of beneficial mutations

Beneficial mutations are the driving force for evolution and have been subject to numerous theoretical studies. Since beneficial mutations are rare, they are difficult to study experimentally. I am using the filamentous fungus Aspergillus nidulans in an environment that reduces its fitness to study beneficial mutations. The spatially structured growth of this fungus on a surface directly reveals the presence of beneficial mutations and allows an experimental study on the distribution of available beneficial mutations versus the distribution of mutations that actually get fixed. Epistasis of beneficial mutations will be measured by combining several spontaneous beneficial mutations into one background.

Analogous to well-known fermented products such as yoghurt, wine, beer and sauerkraut, Zambia has many endogenous fermented products. The fermentation processes are ancient and result in safe products with an increased nutritional value and an increased shelf life than the raw materials. The microbiology of fermentation in these traditional foods is largely unknown and represents an outstanding opportunity for addressing both fundamental and practical questions of wide concern. In particular, why are the microbial communities in these fermented products so stable and what mechanisms prevent the invasion of novel strains such as pathogenic bacteria. These questions represent long-standing issues in community ecology and evolutionary biology, namely, what makes natural microbial communities both diverse and stable over the long-term.

Evolution of antagonistic interactions, the evolution of bacteriocin production by Pseudomonas aeruginosa

Bacteriocins are compounds produced by bacteria and are directed to closely related species. It is known that these compounds have an important ecological function and influence many microbial interactions. Bacteriocins have been suggested as novel antibiotics in medicine. In a survey using 150 clinical isolates of the Pseudomonas aeruginosa, I found that the majority of these isolates can be inhibited by bacteriocin produces by laboratory isolates of P. aeruginosa. This inhibition peaks at intermediate levels of genetic similarity of the producing strain and the targeted strain. In evolutionary experiments, I currently examine to what extent the level of production of these bacteriocins can be a target of selection.